Kou Yoku is clean shaven and has shoulder length hair.
Kou Yoku's personality is similar to that of Shin's: Rude, laid back and intense when it comes to combat, He appears to be an instinctual fighter down to the core.
After the Qin army had successfully conquered the Sanyou region, Kou Yoku and Haku Rei were stationed at the Qin border under the command of General Rin Bu Kun. He went to taunt the Hi Shin Unit with arrows for three days until Shin has enough and jumps from the top of their post on the cliff to slay him, He blocks the attack and they soon begin trading blows. The Chu retreat to stop a battle from breaking out but Shin continues to chase them. Kou Yoku fires arrows at him but Shin easily deflects them before Haku Rei knocked him off his horse with one shot. Shin then tells them the young 1000-Man Commanders of Qin are all monsters and they aren't in the same league. Later, he is scolded by Rinbukun for fighting Shin. He then asked him about Shin's abilities. He responds by saying his was nothing special. Haku Rei then says he is quite strong, but he's no match for Kouyoku with his Bakuya Sword. A few days, later Qin and Chu pull back their forces.
He was present for the meet up between Shun Shin Kun and Ri Boku. After the meeting, Rin Bu Kun asked Shun Shin Kun if Ri Boku was planning a Chu/Zhao Alliance. To which he told them that they were underestimating Ri Boku, because it is something far more terrifying than they could imagine. Months later, he is part of the first wave of Chu forces invading Qin from the border and is shocked when their army encounters the Tou Army.
During the Battle of Kankoku Pass against Qin, Kou Yoku is placed in the Chu 1st Army along with Haku Rei, led by General Rin Bu Kun. He tried to kill Mou Ten, but Mou Ten easily parries his blows. Then he remembered Shin's words about the young 1000-Man Commanders of Qin and was about to pull out his Bakuya Sword but the duel was halted when Roku O Mi came charging in to slay Rin Bu Kun.
Later, when Mouten is about to slay Haku Rei, Kouyoku arrives to parry the blow, knocking Mou Ten off his horse. Before he can kill Mou Ten, Ou Hon arrives to save him and both forces engage each other in battle. Kou Yoku unsheathes his Bakuya Sword and duels Ou Hon. As they clash, word arrives of Rinbukun's death at Tou's hands.
At night, as they cremate Rinbukun’s body, he promises to get revenge by killing Tou.
The next day, he and Hakurei are transferred to the 2nd Army said to be dangerous even for allies; under the command of General Ka Rin. Later that day, everyone from the first army above the rank of 1000-Man Commander was gathered up. They were shocked to meet the giant, cold-hearted General Karin. She calls out Rinbukun's lieutenant Ro Kin. As he pledges his loyalty, she kicks him breaking his neck, saying she has no use for "incompetent fools who reek of baldie." And that if it was up to her, they would all be executed. Also, that she declares that the remnants of the 1st Army fight that day with no assistance from the 2nd Army. And if they are unable to slay Tou they will all be executed. She leaves telling them that if they tell anyone about her height their heads will roll.
During the 15th day of the battle, General Karin, seeing that Tou himself is on the battlefield, promotes Kouyoku to a 5000-Man Commander and orders him to aim for Tou's head. Kou Yoku takes this opportunity to avenge his friend Rinbukun and heads out. In an attempt to sourround the enemy general, Kou Yoku spreads his army while engaging Tou in combat himself. As the two men duel, their armies try to take each other out. This way, Kou Yoku keeps Tou occupied and prevents him from attacking the Ka Rin Army, who has now entered the battlefield as well.
Kou Yoku is heavily offense oriented and a capable swordsman with great hidden potential. Angered by the death of his general Rin Bou Kun, Kou You fought one on one with General Tou for a considerable amount of time which is impressive given that the latter killed his leader a few days before.
Wielding a legendary sword, Kou Yoku has shown himself a capable leader and source of inspiration for his men. Kou Yoku also has shown the capacity for team work combining his unit with Haku Rei's very quicky in order to stall the combined assault of Mou Ten and Ou Hon. After leading a hastily organized 5000 men and holding his own against general Tou, his abilities impressed General Ka Rin who called him "a talent to be nurtured".